But i got this message, and when i send emails it says that my ip is 200.14.251.247 (my wan)

"Your IP address 200.14.251.247 is associated with the domain rdc-net251.zone.Nevertheless your message appears to be sent from mail.tehmcorp.cl.You may want to change your pointer (PTR type) DNS record and the host name of your server to the same value.Here are the tested values for this check:

You're using the wrong command (the domain name part of your dig) and you appear to be getting the wrong answer, it should return the LAN IP of your mail server. Go to the Split DNS wiki article and run all the commands shown in the "Verify....." section of that article. Read the text in that section and it tells you what to expect for the correct output of those commands.